Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$91.40	5.124%	$96.0833	$96.08	$96.10	$96.10
Purchase #2	$147.85	13.237%	$167.4209	$167.42	$167.40	$167.40
Purchase #3	$58.48	7.535%	$62.8865	$62.89	$62.90	$62.90
Purchase #4	$214.41	4.385%	$223.8119	$223.81	$223.80	$223.80
Purchase #5	$46.67	9.274%	$50.9982	$51.00	$51.00	$51.00
Purchase #6	$164.78	10.105%	$181.431	$181.43	$181.45	$181.40
Purchase #7	$250.71	7.783%	$270.2228	$270.22	$270.20	$270.20
7 purchase totals =	$974.30		$1,052.8546	$1,052.85	$1,052.85	$1,052.80